Female gender is associated with increased incidence and severity of whiplash injury, but the reasons underlying this association remain unclear. Models can be used to explain how biomechanical gender differences can lead to differences in head and neck kinematics during whiplash and thus injury. However, analyses of gender differences in whiplash have been limited because there are currently no models which represent the human female neck. The goal of this project is to characterize geometrical differences in vertebrae and muscles in size-matched males and females and 50th percentile females. It is hypothesized that similar sized males and females will have different musculoskeletal geometry. If this hypothesis is true, it will be necessary to develop gender-specific models of females, rather than merely scaling male models. [unreadable] [unreadable] The specific aims of this project are: 1) to characterize the geometry of neck muscles and bones in male and female subjects. Neck muscle and vertebral dimensions will be measured from magnetic resonance images (MRI) and radiographs in male and female subjects who are size-matched in external dimensions and in 50th percentile females; and 2) to quantify gender differences in neck volumes and bone dimensions. Geometric parameters will be compared between genders using t-tests, and regression analyses will determine whether mathematical relationships exist among parameters. This aim will test the hypothesis that males and females have different musculoskeletal geometry. [unreadable] [unreadable] The CDC Research Objective addressed by this project is under Injury Biomechanics: Identify the modifiable risk factors for and mechanisms of nonfatal whiplash injuries of the neck and back. The improved understanding of the mechanisms of whiplash injury will provide information which can aid in design of the preventative measures and treatment protocols. [unreadable] [unreadable]